Skin screw electrodes

ABSTRACT

Electrodes providing excellent recording and physical stability. Electrodes are disclosed that may include a plurality of small teeth that possess a novel design shape and orientation. The shallow and relatively long teeth run parallel to the rim of the electrode that presses against the patient&#39;s skin. When the electrode is twisted onto skin, the tiny teeth penetrate the stratum corneum and move nearly horizontally under the stratum corneum, thus anchoring the electrode securely to the skin. The electrodes cause minimal discomfort to the patient since the small teeth do not extend to the pain fibers which are located in deeper layers of the skin. The electrodes may be fabricated in a variety of geometries including cylindrical, disk, and blunt bullet or top shapes. In some instances, the electrodes may be connected to detachable leads having magnetic properties.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 15/282,828, filed Sep. 30, 2016 and U.S. patent applicationSer. No. 14/359,904, filed Aug. 26, 2014, which is a U.S. National Stageof International Patent Application No. PCT/US2012/024010, filed Feb. 6,2012, which was published in English under PCT Article 21(2), which is acontinuation-in-part of U.S. patent application Ser. No. 12/012,607 (nowU.S. Pat. No. 8,112,139), filed Feb. 4, 2008, and also claims thebenefit of U.S. Provisional Patent Application No. 61/562,483, filedNov. 22, 2011. The entire disclosures of these applications areincorporated herein by referenced.

FIELD OF THE INVENTION

The present invention relates to electrodes that are adapted for fastinstallation and stable implantation into the skin of a subject. Theelectrodes are useful for a variety of physiological recording andstimulation applications.

BACKGROUND OF THE INVENTION

The electrical nature of physiological processes has been known for overa century. The electrical components of neuronal activity and thecontraction of muscles may be recorded using electrodes placed onto thesurface or just below the surface of the skin. Furthermore, excitabletissues, such as nerves and muscles, may be stimulated electrically toachieve various physiological effects.

The electroencephalogram (EEG), as a commonly-utilized diagnostic tool,provides a unique window to observe the functional activity within thebrain. Recent technological advances in electronic and computer systemshave allowed over one-hundred EEG channels to be recorded simultaneouslyand modern signal and data processing techniques have provided newinsights into the recorded data, both in the temporal and spatialdomains. Similar advances have affected the techniques used to recordother electrophysiological events in the body, such as electromyograhy(EMG). Recording of electrophysiological events in the body may beuseful in diagnosing a variety of physiological disorders. For example,EEG allows for the non-invasive measurement of the electrical activityof the brain to diagnose epilepsy, sleep disorders, or determine thestate of the brain during coma. By assessing the entry of a patient intoa sleep state, EEG may also be used to maintain a state of arousal in apatient. EEG in the form of event related potentials (ERPs) is alsocommonly used in clinical neurophysiology to evaluate the functional orcognitive response of the central nervous system to a certain stimulus.Finally, EEG is currently being employed within systems that establishcommunication between the brain and an external device—so calledbrain-computer interfaces.

Despite the recent technological advances and the large number ofpotential applications, affixing EEG recording electrodes onto the scalpof a subject requires a manual procedure which is a long, difficultprocess for both the EEG technician as well as the subject. Hair on skinwill hinder the ability of the electrode to adhere to the patient.Because of body heat drying the electrolytic gel, the electrodeimpedance will increase over time. In addition, due to body motion,snagging of the wire leads, and deterioration of the adhesive,electrodes will often disengage. In light of these difficulties, thelabor and facility usage costs for electrode installation have been asignificant portion of the total cost of clinical EEG studies and havesignificantly hindered the acceptance of large-array EEG in clinicalapplications. In addition, some applications require improved electricalaccess that may be obtained chiefly through the insertion of needleelectrodes under the skin. The insertion may be quite painful for thepatient and is accompanied by a variety of concerns regarding the safetyof the patient.

An additional difficulty encountered during EEG is in the stability ofelectrode attachment to the body. The electrode is connected to a wirelead which in turn runs to the signal recording device. Because of thenatural movements of the patient, the wire leads will often becometangled and pulled by the patient. The electrode will subsequently bepulled off of the skin and require reattachment. The wire leads ofcommon EEG electrodes can also act as tethers which limit the movementof the patient, which in turn limits the potential application of EEGand EMG.

Prior work has attempted to address some of the deficiencies of EEGelectrodes. For example, U.S. Pat. Nos. 6,175,753 and 6,201,982 toMenkes et al. discloses quick-placement EEG electrodes. The electrodesdisclosed in those patents attempt to avoid the problems associated withhair on the patient by actually attaching the electrode to the hair ofthe patient, thereby stabilizing the electrode. The electrodes disclosedby Menkes et al. also include a sponge that replenishes the electrolyticgel for prolonged applications. Nevertheless, the electrodes would stillsuffer from some of the shortcomings of the prior art, includinginconsistent electrical contact with the skin due to eventual drying ofthe electrolyte solutions, physical instability of the electrode, andclinical feasibility of allowing a large number of electrodes to beaffixed to the scalp rapidly.

Thus, there has been a long-standing need for electrodes that may bequickly and securely placed on a patient without requiring shaving ofthe skin or administration of adhesive. In addition, typical electrodeadministration often employs an abrasion step where a layer of the skinis worn off to improve the signal. Such procedures are time consumingand are often uncomfortable for the patient. The electrodes wouldpreferably be stable after implantation and provide excellent electricalcontact to the skin for both recording and stimulation of the tissue inthe area of the electrode, with or without the use of electrolytic gels.

BRIEF DESCRIPTION OF THE DRAWINGS

For the present invention to be clearly understood and readilypracticed, the present invention will be described in conjunction withthe following figures, wherein like reference characters designate thesame or similar elements, which figures are incorporated into andconstitute a part of the specification, wherein:

FIG. 1 displays a schematic of an embodiment of the present invention;

FIG. 2 is a close-up view of the teeth of the electrodes of the presentinvention;

FIG. 3 depicts how an embodiment of the present invention may beattached to the body of a patient;

FIG. 4 shows an electrode of the present invention having a magneticlead;

FIG. 5 shows another electrode of the present invention having amagnetic lead and a plastic electrode body;

FIG. 6A displays the magnetic leads of the present invention;

FIG. 6B displays the use of a magnetic lead with an electrode of thepresent invention;

FIG. 7 depicts an EEG recorded with cylindrical electrodes of thepresent invention;

FIG. 8 displays the impedance variation over time with electrodes of thepresent invention;

FIG. 9 presents another embodiment of an electrode of the presentinvention;

FIG. 10 depicts an embodiment of an electrode of the present inventionthat includes a rubber ring that covers the teeth of the electrodes ofthe present invention;

FIG. 11 is a schematic of how the rubber ring may interact with the skinof a patient;

FIG. 12 presents another embodiment of an electrode of the presentinvention;

FIG. 13 presents another embodiment of an electrode of the presentinvention;

FIG. 14 shows a method by which the electrode displayed in FIG. 12 maybe fabricated;

FIG. 15 depicts a schematic of the electronics that may be used with theelectrodes of the present invention;

FIG. 16A-16D shows multiple configurations of electrodes of the presentinvention that may be used in recording from a patient;

FIG. 17 depicts a cut-away view of a multi-component electrode design ofthe present invention;

FIG. 18 shows a step in a method of fabricating the electrodes of thepresent invention; and

FIG. 19 displays a schematic of an electrode installation device of thepresent invention.

FIGS. 20-23 illustrate portions of representative electrodes suitablefor electrical coupling to a skin surface.

FIGS. 24A-24C are electron micrographs showing electrode teeth (FIG.24A), a single tooth (FIG. 24B), and nanowires on a tooth (FIG. 24C).These stainless steel microscopic teeth are fabricated usingphotolithographic techniques as described herein.

FIGS. 25A-25C illustrate a sensor that includes a disposable disk towhich electrodes are secured.

FIGS. 26-28 illustrate portions of additional representative electrodeshaving flexible extensions so as to attach to a skin or other surface.

FIGS. 29A-29B illustrate portions of additional representativeelectrodes having flexible extensions so as to attach to a skin or othersurface.

SUMMARY OF THE INVENTION

The present invention is directed to recording and stimulatingelectrodes that are easily and stably attached to the skin. The presentinvention provides a simple, effective, and low-cost design that solvesmany of the traditional problems associated with the installation of anelectrode onto the hairy skin of human and animal patients. Theelectrodes of the present invention may include small teeth that possessa novel design shape and orientation. The teeth may be fabricated from ahard metal or other material, as well as be coated or electroplated witha conductive metal or other material to promote effective electricalaccess through the patient's skin. The electrodes of the presentinvention may optionally include a rubber ring that covers and protectsthe electrode teeth when the electrode is not in use.

The plurality of shallow and relatively long teeth preferably runsparallel to the rim or surface of the electrode so that they are able topenetrate the patient's skin effectively, but only to a relativelyshallow depth. When the electrode is twisted onto skin, the tiny teethpenetrate the stratum corneum and move nearly horizontally with respectto the skin surface under the stratum corneum, thus anchoring theelectrode securely to the skin. As such, the electrodes of the presentinvention preferably do not cause pain because the small teeth do notextend to the pain fibers which are located in a deeper layer of theskin, yet the electrodes provide for excellent electrical access to theinterior of the body as well as tremendous physical stability. Theelectrodes of the present invention may be cylindrical, disc-shaped, orshaped in the form of a blunt bullet or top.

In some embodiments, magnetic leads are used to connect the electrodeselectrically with signal processing equipment. The magnetic leads mayconnect to the cap of the electrodes of the present invention that arefabricated from a metal having magnetic properties. In some embodiments,the cap of the electrode may include a socket where a circular magneticlead may be inserted to establish electrical connection between the leadand the electrode. The circular magnet lead may be fabricated from ametal or ceramic material. If the material is ceramic, it is preferablycoated with a metal, such as gold, to ensure adequate electrical contactbetween the electrode and the lead.

Because of their superior physical stability, the electrodes of thepresent invention are well suited to house electronic components thatmay accomplish a wide variety of tasks. For example, the electrodes ofthe present invention may include sensors designed to measure bloodoxygenation, blood glucose levels, or other common physiologicalvariables. The electrodes the present invention may also be usedwirelessly either singularly or as an array so that no electrode leadsextend away from the patient's body, thereby reducing the annoyance ofthe electrode assembly for the patient. Implementation of the presentinvention is particularly appropriate for situations where numerouselectrodes are commonly used, such as EEG or EMG recordings.

The electrodes of the present invention may be fabricated either as asingle integrated unit or as a multi-component system depending on thespecific demands of the application. In certain embodiments, theelectrodes of the present invention may be fabricated using precisionphoto-chemical etching techniques that are well known in the art.

DETAILED DESCRIPTION

It is to be understood that the figures and descriptions of the presentinvention have been simplified to illustrate elements that are relevantfor a clear understanding of the invention, while eliminating, forpurposes of clarity, other elements that may be well known. The detaileddescription will be provided hereinbelow with reference to the attacheddrawings.

The present invention provides electrodes that may be quickly and stablyattached to a patient's skin. The electrodes of the present invention donot require any pre-treatment of the skin to be applied and as suchrepresent a significant improvement over the prior art. In addition, theelectrodes of the present invention may be applied to hairy skin (e.g.,scalp) of a patient. Insofar as the present invention has generalapplicability, as used herein, “patient” refers to both human and animalsubjects who either have a medical condition or are healthy. Theelectrodes of the present invention provide superior physical stabilityand electrical access to the skin of the patient, thus representing asignificant improvement over the prior art. The electrodes of thepresent invention may be employed both as stimulating electrodes andrecording electrodes as detailed hereinbelow.

The electrodes may possess a variety of shapes and geometricalconfiguration of the teeth. The general structure of an electrode 100 ofthe present invention is shown in FIG. 1. The electrode 100 is generallycylindrical in shape with a hollow interior that is capable of housingelectronic components as described further hereinbelow. The electrodes100 may include a magnetic cap 104 attached to a brass plate 106 fromwhich an electrical lead 108 may extend. The magnetic cap 104 may attachto the distal rim 110 (i.e., the portion of the electrode that is awayfrom the skin of the patient) of the electrode, thus forming the outsideportion of the chamber within the body of the electrode. The electrodes100 preferably have a diameter of about 10 millimeter for easy handling;however, the diameter may vary considerably depending on specificapplications. The proximal rim 112 of the electrode (i.e., the portionof the electrode that rests against the skin of the patient) includes aplurality of teeth 116 (shown at higher resolution in FIG. 2) thatextend therefrom.

A higher resolution of the proximal rim of the electrodes of the presentinvention is shown in FIG. 2. In the cylindrical electrode embodiments,the teeth 116 may run parallel to the proximal rim of the electrodethough the specific geometry of the teeth may vary widely. The teeth 116may extend between 0.002 inches and 0.005 inches from the proximal rim112 of the electrode. The teeth 116 may be oriented from about 2° toabout 5° away from the rim 112. The teeth 116 preferably have a sharptip that allows for easy penetration of the epidermis. The length of theteeth 116 may vary widely depending on the particular implementation,with presently preferred embodiments having a length of about 0.005inches to about 0.05 inches with a length of about 0.01 inches beingpresently preferred.

As seen in FIG. 2, at the base of the teeth 116 a small recessed area124 may be present. This recessed area 124 is well suited to capture anyhair that may be present on the surface of the patient's skin. A widevariety of shapes for the recessed area 124 may be used depending on theparticular application where the electrodes are employed. By employingthis configuration, the electrodes 100 of the present invention aresecured to the surface of the skin regardless of the presence of thehair. The electrodes 100 of the present invention thus avoid any needfor manually paring the hair or shaving the patient prior to placement.

The teeth 116 may be of a length and angle such that they are capable ofpenetrating the epidermis to just past the level of the stratum corneum.The specific length, shape, and angle of the teeth 116 of the electrodesof the present invention may be varied widely, with embodiments wherethe teeth 116 penetrate the epidermis past the stratum corneum, thoughpreferably not to the level of pain fibers. Orientation at such a slightangle from the surface of the electrode limits the penetration depth ofthe teeth 116 of the present invention is limited, thereby drasticallyreducing discomfort for the patient. Additionally, the plurality ofteeth 116 forms a sturdy attachment to the skin through the interactionwith the stratum corneum. When piercing the skin (particularly thescalp), the electrodes of the present invention should be appliedquickly to minimize the discomfort to the patient.

By piercing the stratum corneum and reaching the water-containingportions of the epidermis below, the electrodes of the present inventionalso provide excellent electrical access to the patient with electrodeimpedance on the order of 5 kΩ being commonly observed without use ofany electrolytic gels. The electrodes of the present invention may alsobe used with electrolytic gels to improve impedance as the particularsituation warrants. In those instances where an electrolytic gel isused, the electrodes of the present invention may be pressed and turnedlightly into a sheet of hydrogel that contains an amount of ionicelectrolyte compound

The shape, size, and material properties of the teeth may be varied inthe design of the electrodes of present invention. Since the teeth aretypically very small, the material from which the teeth are fabricatedis preferably be both sufficiently hard and stress resistant so that theteeth will not bend or break off during electrode installation.Stainless steel alloy may be effectively employed in fabricating theelectrodes of the present invention in that it achieves an appropriatehardness after annealing. In certain embodiments, the steel alloyincludes a sufficient amount of iron to achieve magnetic permissibilityfor lead wire connection as described below. In other embodiments, theteeth may be coated or electrochemically plated with a conductive metal(e.g., gold or silver) to improve the electrical properties of theelectrodes.

In order to improve performance, the electrode teeth may be coated orelectroplated with a material of low half-cell potential (e.g.,silver-silver chloride), an anti-oxidation metal (e.g., gold), or a highelectron-transfer material (e.g., iridium). The electrodes may befabricated as a single unit made entirely from one type of material. Inother embodiments described below, the body of the electrode may be madeof multiple components including plastic or other non-conductivematerials. In some embodiments, the teeth of the electrode may include anickel-containing alloy (e.g., stainless steel). To reduce thelikelihood or severity of reactions in patients who are allergic tonickel, the teeth of the electrodes of the present invention may becoated with a metal or conductive metal oxide. The electrodes of thepresent invention may be synthesized from a material that is eitherdisposable or autoclavable, thus eliminating cross-infection potentialin human applications.

In some embodiments of the present invention, the electrodes possess theapproximate external dimensions of prior art EEG electrodes (on theorder of 1 centimeter). However, alternative dimensions that aretailored to the specific application may also be employed. For example,if electrodes are to be used on a small patch of skin, a small animal,or applied using an automatic tool, the diameter of the electrode couldbe reduced.

The application of the electrode to a patient's skin may be made byslightly pressing towards the body while turning the electrode 100clockwise as shown in FIG. 3. Accordingly, the electrode 100 is thusquickly and firmly affixed to the patient's skin 404. The application ofthe electrode typically causes no pain since the depth of penetration isnot sufficient to reach the pain receptors located in the deeperportions of the skin. After the electrode is applied to the patient, allof the teeth may extend nearly horizontally under the stratum corneumresulting in a large total electrical contact area and a secureattachment to the skin.

In many prior art electrodes, the electrode lead is permanentlyconnected to the electrode. As the number of electrodes installed on thescalp, for example, increases, the space above the head becomescluttered with wires. In addition, when an electrode lead isaccidentally pulled, the electrodes may separate from the scalprequiring a complete re-installation. The present invention overcomesthese limitations. In certain embodiments, a magnetic disk glued to abrass plate makes electrical contact between the wire lead (which may besoldered to the brass plate) and the electrode as shown in FIG. 1. Assuch, in the present design magnetic attraction may be used to connectelectrodes to the wire leads. This innovation provides a number ofadvantages: 1) electrodes can be easily separated from the leads, makingtheir use convenient for the patient (e.g., for taking a shower orleaving the recording room temporarily); 2) it further facilitates theuse of a hand-held installation devices, as described below; and 3) whenany electrode lead is accidentally pulled, only the magneticallyconnected lead will separate, while the electrode placement on thepatient's skin will not be disturbed. In other embodiments, theelectrode may be fabricated from materials that are not magnetic. Inthose embodiments, the wire lead may be reversibly attached to theelectrode in a variety of manners, such as adhesive, snap joints, orother methods commonly known in the art.

The electrodes of the present invention may also implement a magneticlead 400 in a different manner. The wire lead 404 may be soldered 406 toa magnetic sphere 408 as shown in FIG. 4. The magnetic sphere 408 mayfit into the hole of a paramagnetic cylindrical disk 412 having a holein its face (e.g., a steel washer) that is able to be attached or joinedto an electrode body 416. The cylindrical disk 412 may also befabricated from any other material that possesses magnetic properties.To improve the electrical connectivity between the magnetic sphere andthe washer, the sphere 400 and/or washer 412 may be plated or coated inwhole or in part with an electrically conductive material such as gold.The body of the electrode 504 may also be fabricated from plastic asshown in FIG. 5 to provide a lighter-weight electrode. The plastic body504 may include metal components that create connectivity between theteeth that are placed in the patient and the conductive cap 412. Theplastic body 504 may be attached to the teeth 116 by heat activatedlocks 508 or any other securing mechanism.

The magnetic leads provide for improved ease of use both in storage andapplication. FIG. 6A shows how magnetic leads 408 may be easily storedin a group due to their magnetism or on a metal strip 410 near thepatient. That property allows the leads 408 to be selected individuallyand attached easily to the electrode body 416 as shown in FIG. 6B.

FIGS. 7 and 8 display physiological data collected from patients. FIG. 7shows EEG data collected from a patient using electrodes of the presentinvention. FIG. 8 demonstrates that the impedance using the electrodesof the present invention is relatively stable after placement andimproved compared to standard prior art skin electrodes. Electrodes wereplaced at two scalp sites (C3, C4) on two separate patients (A, B) usingboth prior art disk electrodes (solid lines) and skin screw electrodesof the present invention (dashed lines). The skin screw electrodes ofthe present invention maintained consistent electrical contact duringthe entire experiment as shown. Another embodiment of the electrodes ofthe present invention is shown in FIG. 9. In some embodiments, theelectrode body 430 may have a low disk-like profile. This allows thepatient to wear the electrode more comfortably while sleeping or duringnormal daily activities and would further reduce risks of displacementassociated with inadvertent bumping of the electrode. The disk-likeelectrode 432 may be fabricated having a spherical socket or hole intowhich a magnetic sphere 408 connected to a wire lead 404 may be placed.The disk-like electrode embodiment 430 may also include holes 432 intowhich an applicator apparatus may be inserted. Thus, the practitionerwho applies the electrodes would be able to twist the electrode intoplace even with a low profile of the electrode body. In this and otherelectrode embodiments, the novel teeth of the present electrode may bepresent not only at the rim of the electrode but also in additionalgeometric patterns across the face of the electrode. The teeth may bepresent in concentric circles, rows, or any other configuration usefulfor the particular application. When implemented as concentric circles,the multiple concentric sets of electrode teeth may be electricallyindependent of one another and act as independent electrodes formultiple implementations including the localized measurement of voltagein a patient.

The electrodes of the present invention may also include a rubber ring460 that surrounds the base of the electrode as shown for a disk-likeelectrode body in FIG. 10. While shown for a disk-like electrode body,the rubber ring 460 may be used in all of the geometric configurationsof the electrodes disclosed herein. The rubber ring 460 would bothprotect the teeth 116 of the electrodes from inadvertent bending priorto use and also be useful for moving hair away from the site ofelectrode application as shown in FIG. 11.

An additional embodiment of the electrodes of the present invention isshown in FIG. 12. In this embodiment, the electrode body 550 is shapedlike a blunt bullet or a top. The electrode teeth 116 may be locatedacross the bottom face of the electrode 550 and allow the electrode 550to be attached to the patient across many angles. This embodiment of theelectrodes of the present invention is shown in FIG. 12 with anintegrated wire lead 404. This embodiment is particularly helpful forelectrode placement in curved body areas. The “blunt bullet” embodimentalso is able to penetrate hair easily to provide a strong electrical andphysical connection to patient's skin. This embodiment may also beimplemented in a configuration having a twisting knob 564 at the top forease of attachment to patients. The twisting knob 564 may be magnetic soas to be compatible with the use of the magnetic leads 404 as describedhereinabove. This electrode may include stabilizing legs 568 that reston the skin of the patient and provide additional support for theelectrode once it is attached as shown in FIG. 13.

The “blunt bullet” type electrodes may be formed using a single strip ofmetal. For example, a strip of metal 570 that includes the electrodeteeth may be fabricated using the commonly known technique ofphotochemical etching (or photochemical milling). After a protectionfilm is formed on desired portions of the sheet, a series of chemicaletching will be utilized to form the microscopic teeth of all electrodessimultaneously. Next, each strip 570 will be peeled from the sheet androlled precisely together with a spacer sheet 574 (which has the sameshape but no teeth), as shown in FIG. 14. The strip of metal preferablyhas a profile which, when rolled into a coil, will provide the desiredprofile for an electrode body. For example, in some embodiments, themetal strip may be widest on one side and decrease in width across thelength of the strip. When rolled into a coil, that embodiment willdisplay a profile of a blunt bullet type electrode body 576. The layersof the roll may thus be arranged appropriately so that the blunt bulletshape of the electrode tip and the swirl pattern of the teeth will beboth formed. The rolled sheets may then be fixed or fused in place usingadhesive, soldering, epoxy, or other fixation mechanism, such as aclamping ring 576 as shown in FIG. 14. After rolling, the teeth willpreferably be distributed uniformly across the electrode surface, thoughany distribution of teeth may be obtained by designing the etchingappropriately. An alternative approach to fusing the rolled sheets intoplace is to pre-coat the sheet with a layer of sintering agent andheat-treat the completed rolls using a standard vacuum sinteringprocess. The resulting electrode has a surface with the novel teeth ofthe present invention in a swirl or spiral pattern across its face.While shown in FIG. 14 for a blunt bullet shape electrodes, the sameprocess may be used to fabricate any geometric configuration ofelectrode.

Since the electrode design of the present invention provides anelectrically-shielded space inside the electrode, electronic circuitsmay be placed within this space, converting the passive electrode intoan active device. The signal may be amplified through an amplifierwithin the interior of the electrode where the outer rim is grounded,thus providing an ideal shield from exterior interference. The interiorspace may also contain a small battery and a telemetric circuit (e.g.,RF, infrared, or BLUETOOTH), providing power and transmitting a singlechannel to a nearby receiver (e.g., a cell phone, PDA, other hand-heldelectronic device, or receiver attached to a recording device). Anexample of the circuitry that made be used with the electrodes of thepresent invention is shown in FIG. 15. The electrodes may be used ineither a wired configuration having wire leads or wirelessly for thehigh fidelity collection and transmission of data.

While the implementation of the present invention shown in FIG. 15 isfor recording an electrical signal, the electrodes of the presentinvention, when equipped with the appropriate electronic components, mayalso act as stimulating electrodes. As a stimulating electrode, thepresent invention could be used in a wide variety of situations todeliver small currents to underlying tissues. For example, prior arttechniques such as transcutaneous electrical nerve stimulation (TENS)and percutaneous electrical nerve stimulation (PENS) have been used totreat chronic pain that is not responsive to other treatments. Theelectrodes of the present invention provide a tremendous tool for use inthese applications and may be modified for use in those areas by theinclusion of well-known electronic components and circuitry.

The electrodes of the present invention may also be used in arrays oftwo or more to create ultra-portable, wireless recording devices capableof high fidelity collection and transmission of data. As shown in FIG.16A, two electrodes 600A, 600B may be applied to the scalp of a patient604 with a cable 608 connecting the two electrodes 600A, 600B. In thatconfiguration, the cable 608 may communicate data and power betweenelectrodes 600A, 600B while at the same time acting as an RF antenna. Incertain embodiments, the cable 608 may be shielded, with the shieldacting as the antenna for data transmission and reception. The antennacould be used to transmit the amplified EEG signal to a nearby computeror receiving station using any standard protocol such as BLUETOOTH.

In other configurations, electrodes 620 could be placed in a starpattern (FIG. 16B) with a central unit 624 that may connect to thepatient using the same small teeth as the electrodes 620. The centralunit 624 can be either an electrode or a non-electrode, includingelectronic components such as a switch to turn on or off the device or again control 626. The central unit 624 may also include an infraredlight emitter 628 for the telemetric transmission of data. Multipleelectrodes may also be placed in a loop (FIG. 16C) or a net (FIG. 16D)configuration. By using multiple electrodes, the number of channels ofdata that are recorded simultaneously may be increased. One of skill inthe art will recognize a wide variety of configurations that may beemployed depending on the physiological data that is to be collected(e.g., EEG, EMG, or EKG). As indicated above, the body of the electrodesof the present invention may be fabricated as a single integrated unitmade of one conductive material. In other embodiments, the electrodesare constructed of multiple components with such configurationsproviding a simple manner for the large-scale manufacture of theelectrodes. A side-view of the multi-component embodiment of theelectrode 700 shown in FIG. 17 contains an electrode rim 704 thatincludes the electrode teeth as described hereinabove and a constrainingwall 708 which makes up the remainder of the electrode body. Both theconstraining wall 708 and the electrode rim 704 that includes theelectrode teeth may be cylinders. The constraining wall 708 may have analignment notch 712 along its exterior face. The depth of the alignmentnotch 712 may be set so that the maximum penetrating depth of theelectrode teeth is set to depth D 716 as shown. The constraining wall708 may be fabricated from either metal or plastic as described furtherhereinbelow. In this configuration the rim of the electrode thatincludes the electrode teeth 704 fits tightly over the constraining wall708 such that the two form an integrated electrode body 700. Theelectrodes may be formed as concentric circles

As described above for the blunt bullet-shaped electrode, cylindricalelectrodes may also be fabricated using a similar technique. Theelectrode rim that includes the electrode teeth 704 may be fabricatedusing the commonly known technique of photochemical etching (orphotochemical milling). The repeating pattern of teeth 804 (as alsoshown in FIG. 2) may be printed as an etchant-resistant chemical ontoboth sides of a sheet of metal 800, e.g. stainless steel. The pattern804 may have the design of the opened electrode cylinder. The pattern804 could be repeated multiple times on the same sheet of metal 800,such as shown in FIG. 18A. After the etchant-resistant chemical dries,the metal is exposed to the etching reagent and those portions which arenot protected by the etchant-resistant chemical are eroded. After sucherosion, the remaining metallic strip 808 is in the shape of theproximal rim of the open electrode cylinder including the electrodeteeth. The metallic strip 808 may then be closed and fused usingwell-known techniques, such as tack welding, to form the cylindricalelectrode body. The metallic strip 808 may be formed into a cylinderaround the constraining wall (FIG. 7) to ensure a tight fit between thetwo components and so that the depth of the electrode teeth may be setappropriately.

In other embodiments, the constraining wall may be formed from a plasticmold. In those embodiments, the metallic strip may include holes in thebody of the strip where plastic could flow during molding, therebyforming a strong connection between the two components once the plasticdries. One of skill in the art will recognize variations of thesemethods for the fabrication of the electrodes of the present invention,such as negative etching or standard high-precision machining.

Although the electrodes of the present invention may be appliedmanually, in cases where a large number of electrodes need to beinstalled, the electrode technician might hand-pick individualelectrodes from a container which takes a significant amount of time. Inaddition, it is often desirable to know the exact coordinates of theelectrodes on the patient's body (e.g., scalp) relative to a knownreference point. Although these coordinates can be acquired using aPolhemus sensor, such processes are time consuming for theadministration of a large number of electrodes. In order to addressthese issues, the present invention may also include a “volley gun”-likeelectrode installation device. Since the electrodes of the presentinvention need not have leads attached prior to installation, a pack ofelectrodes of identical size may be loaded into the electrodeinstallation device, greatly reducing the time between electrodeinstallations. The electrode installation device may also be equippedwith a coordinate sensor, e.g., similar to a Polhemus sensor, to recordthe coordinates of each electrode as it is installed on the patient'sskin, taking little extra time during operation.

An example of the electrode installation device 900 is shown in FIG. 19.In this embodiment, the electrode 904 has a non-circular (e.g., squareor hexagonal) central hole 906 that allows the electrode to be twistedby a rod 908. A pack of electrodes 910 is stepped forward by a steppingassembly which may contain a gear 912, and buttons 914 and 916. A spring918 may be utilized to load the next electrode automatically. A positionsensor 920, which may contain a radio frequency (RF) circuit, measureselectrode location and transmits the result (either wirelessly or via awire) to a computer after each electrode installation.

The electrodes of the present invention may be used for variousphysiological recording techniques such as traditional EEG, EKG, EMG,and other electrophysiological applications. The present invention mayalso be used in other applications where the device is not used as anelectrode. Because of the strength with which the electrodes may beattached to the skin, they may be used to anchor another device onto theskin more securely than by employing standard adhesive tape. Forexample, when equipped with the appropriate electronic components, theelectrodes of the present invention may be used to assess a variety ofadditional physiological measures such as blood oxygenation and bloodglucose levels. With a leak-preventive seal, a liquid-form drug may bestored within the chamber of the device and delivered transcutaneously.Drug delivery may also benefit from electrically induced and controlledelectroporation in which a transcutaneous current is utilized to openmicroscopic channels through which drug may be delivered through theskin in a desired amount.

The electrodes of the present invention may also be used to stimulatemuscle tissue. Microcurrent stimulation of muscles may be employed totreat age-related macular degeneration, wound healing, tendon repair,and ruptured ligament recovery. Further, the present invention may beused to stimulate muscle to improve their strength such as in patientssuffering from osteoarthritis or to preserve muscle tone and mass duringextended periods of disuse such as coma or surgery recovery. Electricsimulation of muscles may also be utilized to mimic the effect ofexercise in weight management.

The electrodes of the present invention may be connected to a variety ofelectronic components to enable a diversity of technical and medicalimplementations. Examples include: 1) a game system controlled by theEEG patterns of the player, where those EEG signals are measured usingelectrodes of the present invention; 2) a robotic system that serves aparalyzed patient by employing measurements of patients' EEG and EMGsignals assessed through the electrodes of the present invention; 3) anambulatory EEG recorder employing electrodes of the present inventionfor emergency medical care; 4) an automatic drowsiness monitor for motorvehicle drivers; and 5) a diagnostic tool for animals in a veterinarysetting. The wireless design of the present invention greatlyfacilitates a number of specialized experimental applications, such asunconstrained neurophysiological monitoring during behavior, where it ispreferred for animal or human subjects to have free range of motionwithin an environment.

Those of skill in the art will recognize that numerous modifications ofthe above-described process can be performed without departing from thepresent invention. For example, modification of the specific geometryand spacing of the teeth of the electrodes and variation of theelectronic components coupled to the present invention are considered tobe within the scope of the present invention.

Example Flexible Electrode

In typical applications, electrodes are applied to rough, curved, orother non-planar surfaces and some flexing of the electrodes or thesupport to which electrodes are mounted is desirable. With someflexibility, electrodes can be better secured to a patient, achieve lowelectrical resistances, and reduce any tendency for the electrodes tobreak.

With respect to FIG. 20, an electrode 2000 includes an electrode base2002 having a distal surface 2003 which is provided with representativeteeth 2005-2006 situated on an electrode extension 2004. Typically, thedistal surface 2003 is a rim of a cylinder and the electrode 2000conforms to a cylindrical surface. The electrode extension 2004 extendsopposite a direction 2001 along which the teeth 2005-2006 face, i.e.,opposite a direction in which the teeth 2005-2006 are moved forattachment to a skin surface. An upper edge 2008 of the electrodeextension 2004 and the distal surface 2003 define a gap 2012. Inaddition, the electrode extension 2004 extends from the electrode base2002 so as to define an aperture 2010. As shown in FIG. 20, the upperedge 2008 of the electrode extension 2004 is situated at an angle θ withrespect to the distal surface 2003. The angle θ is shown as a positiveangle and is typically within a range of 0 to 0.5 degrees, 0 to 1degrees, 0 to 2 degrees, 0 to 5 degrees, or 0 to 10 degrees, butnegative angles in these or other ranges can also be used.

As shown in FIG. 20, the electrode 2000 is shown schematically andgenerally not to scale, but the electrode extension 2004, the gap 2012and the aperture 2010 are shown to scale. In other examples, exactdimensions and scaling can be different. Only two teeth are shown, butmore are typically provided. Similarly, only a single electrodeextension is depicted, but one or more can be used for each electrode.The gap 2012 and the aperture 2010 provide flexibility so that whenpressed against a skin surface, the distal surface 2003 (such as anelectrode rim) can conform to a curvature of a scalp surface anddistribute forces more evenly. This generally permits more teeth toengage a skin surface and reduces damage to the teeth. This isparticularly useful for relatively large electrodes. Fabrication of anelectrode such as the electrode 2000 can be done with aphotolithography/etching process as discussed above, with little or noadditional cost.

Referring to FIG. 21, a representative electrode 2100 includes anelectrode base 2102 that includes an electrode extension 2110 situatedat a distal surface 2108. Teeth 2105-2107 extend from the electrodeextension 2110 so as to face an attachment direction 2101. An upper edge2114 of the electrode extension 2110 and the distal surface 2108 definean angle θ that is typically less than 5 degrees. The electrodeextension 2110 defines a gap 2116 from the distal surface 2108.

In another example shown in FIG. 22, a representative electrode 2200includes an electrode extension 2210 that defines a gap 2204 and anaperture 2205 from an electrode base 2202. Teeth 2206-2209 are situatedat a distal surface 2220 of the electrode extension 2210 and face anattachment direction 2201. An upper surface 2216 of the electrodeextension 2210 and a distal surface 2215 are at an angle θ that istypically less than 1, 2, or 5 degrees.

Referring to FIG. 23, a representative electrode 2300 includes anelectrode body 2302 that has representative teeth 2305-2306 situated ata distal surface 2310 of the electrode base 2302. The teeth 2305, 2306face an insertion direction 2301 and define respective relief regions2315, 2316. While FIG. 23 is generally not to scale and only a portionof the electrode 2300 is illustrated, the teeth 2305-2306 are shown toscale. As with other examples discussed above, the electrode 2300 andthe teeth 2305-2306 can be formed in a single piece by aphotolithography and etching process, and multiple electrode strips canbe formed of a single electrode substrate. As with other electrodesdiscussed above, it is generally convenient to form the teeth and otherelectrode portions with a single electrode substrate, but electrodes andteeth can be formed separately and teeth attached to the electrode, butthis is generally less suitable than unitary construction. To provideadditional flexibility, the electrode body 2302 includes one or moreapertures such as apertures 2320. In this example, the apertures 2320are slits elongated in a direction parallel to the insertion direction2301, but slits in other directions can be used. Apertures can becircles, squares, rectangles, or other shapes with curved or straightsides, and can be arranged in an array or randomly in the electrode body2302. Typically such apertures are situated in portions of the electrodebody 2302 that are closer to the distal surface 2310.

Representative fine teeth or hooks for connection to a top layer of skin(stratum corneum) or other surface are shown in FIGS. 24A-24C. FIG. 24Adepicts fine teeth and FIGS. 24B-24C show nanowires covering the teeth.Nanowires can be conveniently provided for electrical connections, butare not required. In some examples, the nanowires are formed of zincoxide or gold. The teeth are designed to secure the sensor on the skinand electrically connect to the skin. The teeth are generally made ofstainless steel, and gold coated to reduce an impedance of theskin-electrode-interface. As used herein, a tooth depth is a toothdimension associated with a maximum tooth extension from an untoothedportion of a surface, and tooth depths of less than 1 mm, 0.5 mm, and0.25 mm are preferred.

Referring to FIGS. 25A-25C, a sensor 2500 incorporating electrodes asdescribed herein includes a housing 2502, shown as a cylindricalhousing, that defines a volume in which circuit components such as A/Dconvertors, amplifiers, buffer circuits, microcontrollers, RFtransmitters (or transceivers, analog switches, batteries, circuitboards, and other components can be situated. A power switch 2504 (suchas push-button switch) is provided on an end surface 2501 of the housing2502 at an upper end and can include an indicator light such as an LEDto aid the user in determining that the sensor 2500 is active. Aperimeter surface 2503 can be knurled or otherwise provided with gripelements, preferably surface features that extent along a central axisof the housing 2502. Other grip aids or grip promoting materials can beused instead on in addition to knurling. The housing 2502 is preferablyliquid proof to permit sterilization. A disposable disk substrate 2505(typically a plastic disk) is situated at a distal end of the housing2502 and attachment electrodes such as representative attachmentelectrodes 2510-2512 that include representative toothed distal surfaces2520-2522 are secured to the disk substrate 2505. Each of the attachmentelectrodes 2510-2512 is shaped in a boot form to allow slight motion ina vertical direction so as to conform to a subject scalp surface.Typically, the electrodes 2510-2512 approximately conform to thecylindrical shape of the perimeter surface 2503, and define respectivegaps 2530-2532 that separate electrode end portions form the diskelectrode 2505. For example, as shown in FIG. 25B, the electrode 2511includes an end portion 2511B and a portion 2511A that is secured to thedisk substrate 2505, and the gap 2531 is situated between the endportion 2511B and the disk substrate 2505. Other electrodes aresimilarly constructed and secured. This electrode shape can be referredto as boot-shaped, and permits electrode flexing to conform to a subjectsurface. Typically one, two, three, four or more electrodes areprovided, but for convenient illustration, only three electrodes areshown in FIGS. 25A-25B. In some examples, the electrodes are formed of25 μm thick gold-plated stainless steel but other conductors andthicknesses can be used. As noted above, housings need not becylindrical but can have rectangular, polygonal, ellipsoidal or othercross-sections.

Referring to FIG. 25C, clip posts 2540-2542 are fixed to the disposabledisk substrate 2505 to retain a battery such as a coin-shaped battery oneither surface of the disk substrate 2505 and to couple electrical powerto sensor circuitry. The disk substrate 2505 can be provided withconductors situated to couple each of the electrodes to suitable circuitelements as discussed above, typically one or more analog switchesand/or amplifiers. The distal surface 2521 of the electrode 2511 canhave surface features such as shown in FIGS. 24A-24C. Typically teethare formed that are 30-50 μm high at an angle of 2-5 degrees from theplane defined by the disk substrate 2505, and include a plurality ofnanowires. In the arrangement of FIGS. 25A-25C, the disk electrodes 2505can be disposable, and typically the entire disk assembly of FIG. 25C isdisposable.

In the example of FIGS. 25A-25C, the electrodes 2510-2512 are separatedalong the perimeter of the disk 2505 by gaps 2535-2536. A representativesection 2550 of the electrode extension 2511 includes teeth such asillustrated in FIGS. 24A-24C.

With respect to FIG. 26, an electrode 2600 includes an electrode base2602 having a distal surface 2603 which is provided with representativeteeth 2605-2606 situated on an electrode extension 2604. Typically, thedistal surface 2603 is a rim of a cylinder and the electrode 2600conforms to a cylindrical surface. The electrode extension 2604 extendsalong a direction 2601 along which the teeth 2605-2606 face, i.e., alonga direction in which the teeth 2605-2606 are moved for attachment to askin surface. An upper edge 2608 of the electrode extension 2604 and thedistal surface 2603 define a gap 2612. In addition, the electrodeextension 2604 extends from the electrode base 2602 so as to define anaperture 2610. As shown in FIG. 26, the upper edge 2608 of the electrodeextension 2604 is situated at an angle θ with respect to the distalsurface 2603. The angle θ is shown as a positive angle and is typicallywithin a range of 0 to 0.5 degrees, 0 to 1 degree, 0 to 2 degrees, 0 to5 degrees, or 0 to 10 degrees, but negative angles in these or otherranges may be preferred for this orientation, in contrast to the exampleof FIG. 20.

Only two teeth are shown in FIG. 26, but more are typically provided.Similarly, only a single electrode extension is depicted, but one ormore can be used for each electrode. The gap 2612 and the aperture 2610provide flexibility so that when pressed against a skin surface, thedistal surface 2603 (such as an electrode rim) can conform to acurvature of a scalp surface and distribute forces more evenly. Thisgenerally permits more teeth to engage a skin surface and reduces damageto the teeth. This is particularly useful for relatively largeelectrodes. Fabrication of an electrode such as the electrode 2600 canbe done with a photolithography/etching process as discussed above, withlittle or no additional cost.

Referring to FIG. 27, a representative electrode 2700 includes anelectrode base 2702 that includes an electrode extension 2710 situatedat a distal surface 2708. Teeth 2705-2707 extend from the electrodeextension 2710 so as to face an attachment direction 2701. An upper edge2714 of the electrode extension 2710 and the distal surface 2708 definean angle θ that is typically less than 5 degrees. The electrodeextension 2710 defines a gap 2716 from the distal surface 2708. As shownin FIG. 27, the teeth 2705-2707 and the electrode extension face acommon direction (the insertion direction 2701), but other orientationscan be used. A tip 2720 of the electrode extension is situated to facein a common direction with the teeth 2705-2707.

In another example shown in FIG. 28, a representative electrode 2800includes an electrode body 2802 that includes electrode extensions 2804,2806 that define apertures 2805, 2807. Teeth such as representativeteeth 2810, 2811 are situated at a distal surface of the electrodeextensions 2804, 2806. The electrode extensions 2804, 2806 extend fromthe electrode body 2802 so as to form closed apertures that can becircular, polygonal, ovoid, or other shapes. Only selected teeth areshown for convenient illustration. A front facing portion 2820 and aback facing portion 2832 of the electrode extension 2806 and other suchextensions can be provided with teeth that face in different directions,if desired, so that the electrodes can be secured by motion along oropposite a direction 2801.

FIG. 29A illustrates an additional example electrode 2900 that includesan electrode body 2902 having a distal surface 2904. An electrodeextension 2906 is coupled to or extends from then distal surface and isformed so as to define gaps 2910, 2912 between the distal surface and afirst extension portion 2911 and between the first extension portion2911 and a second extension portion 2913. A distal surface 2916 isprovides with one or more teeth 2931-2934 that are oriented forinsertion into skin or other surface in a direction 2901. In furtherexamples, additional extension portions and gaps are provided. Theelectrode 2900 is typically formed of a single sheet of a conductorhaving a common thickness. Dimensions of the electrode extensionportions can be selected as convenient, generally to provide suitableflexibility for attachment. In the example of FIG. 29A, a proximalsurface of the second extension portion 2913 and a distal surface of thefirst extension portion 2911 are at an angle θ the such that |θ|≦1, 5,10, or 20 degrees. Similarly, extension portion widths (approximatelyalong a Y-axis as shown) and lengths (approximately along an X-axis asshown) can be the same or different. A slightly different arrangement isillustrated in FIG. 29B in which distal and proximal surfaces of theelectrode extension portions and the distal surface of the electrodebody are parallel.

1. An electrode for attachment to skin of a patient, comprising: anelectrode body having a proximal surface and a distal surface; aplurality of electrode body extensions situated at the distal surface ofthe electrode body that define respective openings between the distalsurface of the electrode body and proximal surfaces of the electrodebody extensions, wherein each of the plurality of electrode bodyextensions includes at least one tooth situated on a distal surface ofthe respective electrode body extension.
 2. The electrode of claim 1,wherein each of the electrode body extensions includes a respectiveextension tip that is situated so as to face in a direction opposite adirection faced by the teeth.
 3. The electrode of claim 1, wherein eachof the electrode body extensions includes a respective extension tipthat is situated so as to face in a direction that is the same as adirection faced by the teeth.
 4. The electrode of claim 1, wherein eachof the plurality of electrode body extensions includes a plurality ofteeth.
 5. The electrode of claim 4, wherein each of the plurality ofelectrode body includes teeth facing in opposite directions.
 6. Theelectrode of claim 4, wherein the each of the electrode extensionsconnects to the electrode body at a first location and a second locationso that the openings define respective apertures.
 7. The electrode ofclaim 6, wherein the apertures are defined in part by a linear sectionand an arcuate section.
 8. The electrode of claim 4, wherein theopenings include an aperture that extends into the electrode body and aslot such that a proximal surface of the electrode extension thatdefines the slot faces the distal surface of the electrode body.
 9. Theelectrode of claim 8, wherein the slots taper so as to widen from theapertures to the tips of the electrode extensions.
 10. The electrode ofclaim 9, wherein the slots taper away from the distal surface of theelectrode body at an angle of between +1 degree and +5 degrees.
 11. Anelectrode assembly, comprising: an electrode substrate; and at least oneelectrode secured to the electrode substrate, the at least one electrodehaving an electrode body with a plurality of flexible extensions at adistal surface, wherein each of the flexible extensions has a pluralityof teeth at a distal surface of the flexible extension.
 12. Theelectrode assembly of claim 11, wherein the electrode substrate is acylindrical substrate and the at least one electrode is secured to aninternal or external surface of the cylindrical substrate.
 13. Theelectrode assembly of claim 12, wherein the cylindrical substrate is ahollow cylindrical substrate.
 14. The electrode assembly of claim 11,wherein the electrode substrate is a disk, and the at least oneelectrode is secured to the disk at a perimeter of the disk so that theteeth extend away from a distal surface of the disk.
 15. The electrodeassembly of claim 14, wherein the at least one electrode includes anattachment portion coupled to a disk perimeter disc and the flexibleextensions define gaps between a distal surface of the electrode bodyand proximal surfaces of the flexible extensions.
 16. The electrodeassembly of claim 11, wherein each of the flexible extensions is bootshaped so as to be conformable to a scalp surface.
 17. The electrodeassembly of claim 11, wherein the at least one electrode includes afirst electrode and a second electrode.
 18. The electrode assembly ofclaim 11, wherein each of the flexible extensions has at least first andsecond electrode extension portions that define gaps between the firstelectrode extension portion and the electrode body and between the firstelectrode extension portion and the second electrode extension portion,wherein the first extension portion extends from the electrode body andthe plurality of teeth are situated at a distal surface of the secondflexible extension portion.
 19. A method of fabricating an electrode,comprising; applying an etchant-resistant chemical to a surface of asheet of conductive material in a pattern that includes a plurality offlexible electrode extensions and a plurality of teeth on the flexibleelectrode extensions, wherein each of the teeth face a common direction;etching the patterned sheet of conductive material so as to define anelectrode so that the plurality of flexible electrode extensions and theplurality of teeth on the flexible electrode extensions are situated ona distal surface of the electrode face.
 20. The method of claim 19,further comprising forming a least a portion of the etched patternedconductive material into a cylindrical section such that the distalsurfaces of the electrode extensions face an axis of the cylinder. 21.The method of claim 19, wherein the flexible extensions are boot shapedportions of the conductive sheet.